Dominant XBB 1.16 variant unable to evade T-cell immunity: Experts

Pune district has seen a surge in daily Covid-19 infections linked to the highly contagious XBB 1.16 recombinant Omicron virus. The ability of the virus to evade natural and vaccine-induced immunity is leading to the spike in cases. However, according to the experts, the virus is unable to evade the T-cell mediated cellular immunity due to which the number of severe patients and hospitalisation remains low.

Researchers at BJ Medical College (BJMC) claim the immune cells called, T-cells tend to recognise parts of SARS-CoV-2 that don’t mutate rapidly. T-cells coordinate the immune system’s response and kill cells that have been infected with the SARS-CoV-2 virus. Lack of evasion of this T-cell mediated cellular immunity by SARS-CoV-2 is thought to be the reason behind less hospitalisation and severe cases among Covid-19 infected patients.

Dr Rajesh Karyakarte, head of Microbiology department at BJMC and state coordinator for genome sequencing said that most Covid-19 patients who are infected this year are vaccinated. They are still getting infected as the new variant is able to evade the vaccine induced immunity or hybrid immunity in these individuals. “The good part is that the number of patients hospitalised or with severe Covid-19 symptoms is less in comparison to the number of infected patients. This is because of the T-cell mediated cellular immunity which the XXB 1.16 variant is unable to evade,” said Karyakarte.

The first case of XBB1.16 recombinant strain was detected in Pune on February 3.

Dr Karyakarte added, “Patients admitted to the hospital have to be closely monitored to see their response to the line of treatment, oxygen requirement. A detailed study has to be conducted in the coming days of the individuals infected with the new strain.”

In the past three months (January-March) Pune district has reported 2,011 Covid-19 cases and three deaths. The district reported 148 cases in January, 157 cases in February and 1,715 cases in March. Currently there are 758 active Covid cases in the district, out of them 26 patients are hospitalised and 732 are in home isolation. However, a majority, 720 patients infected this year have taken at least two vaccine doses of Covid vaccine, said, Dr Abhay Tidke, additional district health officer.

According to Bhagwan Pawar, Health Officer of Pune Municipal Corporation (PMC), individuals with weaker immune systems or medical conditions like hypertension, diabetes, obesity among others should consult with doctors if they develop Covid-19 symptoms. “Spike in Covid-19 cases can be attributed to the new variant.The reason might be the immunity waning out or the virus being able to evade the immunity. We suggest citizens take the booster doses for the virus. However, we will not see as many hospitalisations or deaths as in previous waves of Covid-19,” he said.